Sheathed heating unit



June 15 1926.

F. THORNTON, JR

SHEATHED HEATING UNIT Filed April 29 1924 INVENTOR Pan/f 77mm to, Jfl

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TTORNEY Patented June 15, 1926.

UNITED STATES FRANK THORNTON, JQK, OF PITTSBURGH PATENT OFFICE.

, PENNSYLVANIA, ASSIGNOB ro wns'rmo- HOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION 01 PENNSYL- VANIA.

SHEATHED HEATING UNIT.

Application filed April 29, 1924. Serial No. 709,713.

My invention relates to electric heating devices and particularly to sheathed heater units.

The object of my invention is to provide a relatively simple method of constructing a sheathed heater unit.

In practicing my invention, I provide a tubular metal sheath and locate within it a helically wound resistor wire. Granular electric-insulating and heat-conducting material is fed into the sheath and compacted therein by mechanical means, while the sheath is heated locally at the point where the material is being compacted, to cause lateral expansion thereof. Upon cooling of the sheath, it contracts and the longitudinally compacted material is still further compacted laterally of the tube.

In the single sheet of drawings,

Figure 1 is a view, in front elevation, of a resistor member comprising a part of the heater unit embodying my invention,

Fig. 2 is a view, partially in front elevation and partially in longitudinal section, of a heater unit embodying my invention,

Fi 3 is a view, in longitudinal section, of a heater unit embodying my invention in course of manufacture,

Fig. 4 is a view in side elevation of a mechanical means for compacting the granular material employed, and

Fig. 5 is a top plan view thereof.

A resistor member 11 comprises a wire of any suitable or desired diameter and length, that is wound to substantially helical form upon a suitable mandrel (not shown} and the turns thereof are slightly and uniformly separated from each other substantially as shown in Fig. 1 of the drawin The end portions of the resistor member 11 are straight and extend substantially longitudinally of the helically wound coil.

The formed resistor member 11 is placed within a tubular metal sheath 12 that may be of any suitable or desired shape, in lateral section, and is shown in the drawings as bein of circular section.- The length of the tu ular sheath 12 is slightly greater than the helically wound portion thereof, the excess length at each end thereof being employed for receiving supporting and terminal members therein. 1

A terminal member 13 that may be of any suitable or desired type of construction and that is illustrated in Figs. 2 and 3 of the drawing as comprising a tubular member having an axial opening therethrough of substantially the same size as the wire 11, extends partially into the tube 12 and is insulated therefrom by a tubular member 14, of a suitable electric-insulating material, such as mica. Any suitable or desired means of effecting close operative engagement between the end of the resistor wire 11 and the terminal member 13 may be employed and, while I have illustrated a specific embodiment of terminal member and of means for supporting the same in the respective ends of the tubular sheath, I do not desire to be restricted thereto, as any suitable or desired construction of terminal may be-employed.

In the construction of the heating unit one terminal member 13 may be mounted on its co-operating end of the resistorwire and be placed within the one end of the tubular sheath 12, the insulating member 14 being employed as hereinbefore stated. This construction closes the heretofore open end of the tubular sheath 12 at one end thereof. which is made the lower end of the heating unit during further operations thereon. The unfinished heater unit comprising the tubular sheath 12, the resistor member 11 and the lower terminal member is placed in a suitable machine (not shown) in a substantially upright position.

The machine comprises a suitable means for holding the unfinished heater unit,

means for feedingogranular electric-insulating and head-conducting material 15 into the tubular sheath, and comprises further a mchanicallv actuated tamper or hammer 16 that is illustrated more particularly in Figs. 4 and 5 of the drawings. Asthere illustrated, the upper end of the member 16 is relatively narrow, and the lower end is of substantially tubular form, the inner diameter thereof being slightly greater than the external diameter of the helically wound portion of the resistor member 11. Means (not shown) are provided for reciprocatin the member 16 in a substantially vertica direction. As the granular material 15 is fed into the sheath 12 at a predetermined ma, the hammer 16 compacts the material longitudinally of the sheath 12 and the actuating mechanism is so designed that the hammer 16 moves vertically upwardly in accordance with ed 'by. any suitable adjustable mounting.

means illustrated in the drawing, as comprising a pair of cables 18 and 19 that extend vertically upwards from a suitable supporting member 21 surrounding the coil 17, and extending over a pair of pulleys 22 and 23 to asuitably larger pulley 24 that is actuated by any suitable means (not shown) to raise the coil 17 inaccordance with the rise in position of the hammer 16, so that the tube 12 will be heated and caused to expand tively excessive degree in .of the granular ployed, such,

The temperature to which the sheath is laterally at the point thereof where the lower end of the hammer is compacting the granular material.

I have illustrated, in Fig. 3 of the drawing, the tube 12 as being enlarged to a relaorder to bring out more clearly the action of this local heating of successive portions of the tubular sheath.

As hereinbefore stated, the hammer or tamper'16 effects a longitudinal compacting material fed into the tube and it is evident that upon cooling of the tube and its consequent contraction, the granular material isagain compacted, this time in a direction laterally of the tube and of the heater unit.

Any suitable or desired means for locally heating successive may be employed, and I may use a: resistor member of such shape as to or surround the tube or, as illustrated in Fig. 3 of the drawing, I may employ a coil that is" traversed by a suitablealternating current to cause heating of the coilby eddy currents generated therein. It is obvious, of course, that other means may be emforexample, as a gas flame.

heated is greater than that to which, it is subjected in normal operation thereof, to

insure that the refractory material will rernaln in its highly compacted condition dur- 1 111g operation thereof.

Ashereinbefore stated, the granular material is fed into the tubular sheath at a predetermineghrate and is compacted, not only around the resistor member, but also inside thereof, not only by the hammer, but also by the lateral contraction of the temporarily locally heated tubular sheath. As

' the tubular hammer is of such dimensions interiorly thereof as to loosely surround the hehcally wound resistor and is of such, dimensions exteriorly thereof as to'loosely fit intothe sheath, it is obvious that the resistor member is held in proper and uniformly spaced position within the sheath during the manufacture or construction of and scope of the invention,

portions of the tube.

closely encircle theatre the heater unit and isthereafter held in its proper operative position co-axially with the tubular sheath by the compacted granular electro-insulating material, which may comprise magnesium oxide.

When substantially all of the hehoally wound portion of the resistor member has been surrounded by the granular compacted material and also a portion of the straight part thereof at the upper end, the upper terminal member, substantially the same as hereinbcfore described; may be placed in its proper operative position, the same manner as was forth for the contact terminal located at the other end thereof.

An attendant advantage of my hereinbefore described method of obtaining a relatively high degree of compactness of the granular electric-insulating and heat-conducting material is that the tubular sheath is annealed over substantially its entirte length, thereby permitting of bending it in any desired manner in order to allow of intimate'operative engagement with a curved surface to be heated or to permit of its being bent to any desired form to obtain a relatively compact heater unit.

Various modifications and changes may be made without departing from the spirit I- desire, therelimitations shall be imposed by the prior fore, that only such placed thereon as are art.

lt claim as my invention:

1; The method of constructing a sheathed heater unit that comprises the compactingof refractory electric-insulating material around a resistor member within a metal sheath that is locally temporarily heated at the point where the refractory material is being compacted.

2. The method of constructing a sheathed heater unit that comprises the local oompacting of initially granular electric-insulating material around a. resistor member within a metal sheath while said sheath is caused to temporarily expand at the points where the granular material is being compacted. 3. The method of constructing a sheathed heater unit that comprises the local compacting of initially granular electric-insulating material around a resistor member within a metal sheath while said sheath is heated andis thereby caused to temporarily expand at the point where the granular material is being compacted and permitting said sheath to cool to still further compactsaid granular material. Y

4. The method of constructing a sheathed heater unit that comprises placing a resistor member in a metal sheath having a plug at its lower end, compacting by mechanical means, granular electric-insulating material 7 fed into said sheath, causing said sheath to in substantially hereinbefore set' be heated locally at successive points to cause it to expand and permitting said sheath to cool to still further compact said material.

5. The method of constructing a sheathed heater unit that comprises the compacting of granular electric-insulating material around a resistor member within a metal sheath while said sheath is temporarily heated locally at the point where said material is being compacted, to a temperature higher than that to which it will be subjected in actual operation.

6. The method of constructin a sheathed heater unit that comprises the ongitudinal compacting of granular electric-insulating material around a resistor member within a metal sheath, causing a lateral expansion of said sheath at the point where said material is being compacted and permitting said sheath to contract,.to com t said initially compacted material laterallg of said sheath.

7. The method of constructing a sheathed heater unit that comprises placing a helically wound resistor in a tubular metal sheath, plugging the lower end of said sheath, temporarily heating successive restricted portions of said sheath to a temperature hi her than that to which it will be subjecte in actual operation and compacting granular electric-insulating material around said resistor at the point where said sheath is heated.

In testimony whereof, I have hereunto subscribed my name this 16th day of April FRANK THORNTON, JR. 

